Cross-sensitivity—response to non-target gases—drives false alarms and compliance risk. No EC, MOS, or NDIR sensor is perfectly specific, but coefficients, lab matrices, and fusion materially improve reliability. Senseiot shares field-proven assessment and compensation practices in this guide.
Physical Origins of Cross-Sensitivity
EC: catalysts react with similar molecules—CO cells respond to H₂; side reactions and temperature amplify interference.
MOS: most reducing gases drop resistance—CO, H₂, VOC, alcohol look alike; oxidizers move the opposite way.
NDIR is selective but hydrocarbon overlap and water bands need manufacturer interference tables.
Reading Datasheet Coefficients
Vendors express "<X ppm A equals Y ppm target B>"—match test T/RH/pressure to site conditions.
Coefficients are often linear approximations; small cross-terms near alarm thresholds matter—run margin analysis.
Compare brands in the Product Catalog; safety loops may need third-party reports.
Lab Cross-Sensitivity Workflow
Fix target gas in a chamber; step interferents (H₂, ethanol, SO₂, NO₂, extreme RH) and log Δoutput.
Build matrix **S** so **reading ≈ S·c**; invert with least squares or constrained solvers for true concentrations.
Retest on model changes or new solvents—Request a Quote for lab services.
Hardware Mitigation
Filter cartridges remove H₂S/SO₂ while passing CO—replace on schedule with drop or color indicators.
GC/laser for lab truth; field tiering uses "MOS broad + EC confirm."
Sampling location and dilution reduce transient VOC spikes.
Software Compensation and Alarms
Fusion rules: MOS rises without EC CO → VOC not leak; correlation beats single thresholds.
Delay and slope criteria: leaks persist; VOC pulses decay in 30–120 s.
Log interference events—Industry Applications alarm templates.
Standards and Compliance Tests
EN 50291, UL 2034, IEC 60079-29 define cross tests—certification ≠ all solvent environments.
Deployment questionnaires should capture adjacent processes.
Senseiot favors certified cores—Product Catalog.
Operations and Continuous Improvement
Close the loop: false alarm → interferent ID → matrix update → OTA; seasonal retune for heating CO or summer O₃.
Train staff on cleaners, pesticides, weld smoke— not every alarm means dead sensor.
Custom matrices and cartridges—Request a Quote from Senseiot.